The 7120 standalone configurations allow a single chain of 1 or 2 disk shelves. Write-optimized (Logzilla) SSDs are not supported in the expansion storage for the 7120. The disk shelves must be fully populated with 24 HDDs. Half-populated shelf configurations are not supported. For more information, see Connecting to Attached Storage. See also Disk Shelf Hardware Overview for component specifications and diagrams.